错误:未在此范围内声明"enumElement" [英] error: 'enumElement' was not declared in this scope

问题描述

我写了以下小脚本:

#include <string>
#include <iostream>
#include <cstdlib>
using namespace std;
int main() {
    enum class Day {sunday, monday, thuesday, wednesday, thursday, friday, saturday};
    Day unusedDay, today = sunday;
}

但是我有一个问题.当我调试程序时，编译器会说:

But i have a problem. When I debug the programm, the compiler says:

error: 'sunday' was not declared in this scope

但是有我的枚举类.为什么不宣布星期日?我该如何更改?

but there is my enum class. Why sunday isn't declared? How can I change that?

感谢answears:)

Thanks for answears:)

推荐答案

您正在将枚举与枚举类混淆.假设您的代码是这样的:

You are confusing an enum with an enum class. Suppose your code was this:

enum Day {sunday, monday, thuesday, wednesday, thursday, friday, saturday};
Day unusedDay, today = sunday;

然后将编译上面的代码，因为普通的 enum 具有在全局范围内可见的值，因此您可以像 Day usedDay，today = sunday; 这样访问它们.至于 enum class es，规则有所不同.为了使您的示例正常工作，您需要编写如下代码:

Then the above code would compile, since normal enum's have values that are visible globally, so you can access them like Day unusedDay, today = sunday;. As for enum classes, the rules differ a little. For your example to work, you would to write the code like this:

enum Day {sunday, monday, thuesday, wednesday, thursday, friday, saturday};
Day unusedDay, today = Day::sunday;

如果您查看 enum 与vs enum类 es的文档，则会看到以下内容:

If you look at the documentation for enum's vs enum classes, you see this:

枚举

声明一个无作用域的枚举类型，其基础类型不固定-

Declares an unscoped enumeration type whose underlying type is not fixed -

请注意此处使用 unscoped 一词，这意味着该变量的名称就可用.

Note the use of the word unscoped here meaning the variable is available just with it's name.

枚举类

声明一个作用域枚举类型，其基础类型为int(关键字class和struct完全等效)

declares a scoped enumeration type whose underlying type is int (the keywords class and struct are exactly equivalent)

如此处所示，枚举类是作用域的，并且只能作为 enumname :: value ;

As seen here, an enum class is scoped, and accessibly only as enumname::value;

(源)

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